DNA Replication Errors Drive Genome‐Wide Small Inverted Triplication Dynamics

Key findings from this study

This research indicates that:

• FEN1 deficiency strongly associates with small inverted triplication formation in cancer genomes.
• SIT breakpoints preferentially occur at nucleosome midpoints and Okazaki fragment termini, implicating replication machinery in their origin.
• DNA polymerase slippage over hairpin structures provides a mechanism for precise SIT elimination and resolution.

Overview

Analysis of 1,340 cancer genomes identified 4,608 small inverted triplication events and established FEN1 as strongly associated with their incidence. Long-read sequencing in yeast FEN1 mutants and bacterial plasmid systems revealed mechanistic pathways governing SIT formation through DNA replication errors.

Methods and approach

Researchers analyzed cancer genome data to catalog SIT events and identify genetic associations. Long-read sequencing characterized SIT structures in FEN1-deficient yeast cells. PacBioR annotation tools were developed for precise SIT mapping. Plasmid-based E. coli systems examined SIT elimination mechanisms.

Results

SIT structures exhibited consistent dimensions: central duplications and inversions averaging 148/160/148 bp with 30 bp spacer sequences and 6 bp breakpoint junctions. Breakpoints preferentially localized to nucleosome midpoints and aligned with Okazaki fragment termini, indicating replication-dependent origin. DNA polymerase slippage over hairpin structures derived from SIT sequences drove precise plasmid elimination in bacterial systems, demonstrating an active removal mechanism.

These findings establish that SIT formation occurs during DNA replication, particularly in contexts of compromised FEN1 function. The structural regularity across independent events and the reproducibility of SIT elimination through polymerase slippage suggest conserved mechanistic pathways. The association between breakpoint positions and replication landmarks further supports replication fork instability as the primary driver.

Implications

Understanding SIT origination mechanisms provides molecular context for structural variant diversity in human populations and disease-associated genomes. The connection between FEN1 deficiency and SIT accumulation may inform investigation of cancer-associated replication stress pathways. Polymerase slippage as an elimination mechanism suggests potential strategies for modulating structural variant stability.

The PacBioR tool enables systematic annotation of SITs in additional datasets, facilitating future studies of genome rearrangement mechanisms. Identifying nucleosome and replication-based positioning patterns may clarify how chromatin architecture influences structural variant formation genome-wide. These mechanistic insights extend understanding of how DNA replication errors contribute to genomic instability underlying phenotypic variation.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.